Soil Ecology and Tree Health:  Implications for Management of Urban Forests and
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Soil Ecology and Tree Health: Implications for Management of Urban Forests and Ornamental Landscapes. Dan Herms Department of Entomology The Ohio State University Ohio Agricultural Research and Development Center [email protected] Acknowledgements: Students and Post-Docs

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Dan herms department of entomology the ohio state university

Soil Ecology and Tree Health: Implications for Management of Urban Forests and Ornamental Landscapes

Dan Herms

Department of Entomology

The Ohio State University

Ohio Agricultural Research and Development Center

[email protected]


Dan herms department of entomology the ohio state university

Acknowledgements:

Students and Post-Docs

Jim Blodgett, Rodrigo Chorbadjian, Carolyn Glynn, Bethan Hale, Nate Kleczewski, Joe LaForest, John Lloyd, Marie Egawa

Collaborators

Enrico Bonello, Robert Hansen, Harry Hoitink, Bill Mattson, Ben Stinner

Funding Sources:

TREE Fund

USDA National Urban Community Forestry Advisory Council


Dan herms department of entomology the ohio state university

The Ornamental Landscape as an Ecosystem:

Implications for Pest Management

Herms et al. (1984) J. Arboriculture 10:303-307.

“Understanding the ecological interactions between the biotic and abiotic factors within a landscape enables more effective management of pests.”


Dan herms department of entomology the ohio state university

Objective:

Understand how trees allocate their resources in

different environments, and the implications for

the care of trees.

Approach:

Develop framework based on carbon allocation that can be used to predict tree behavior in different environments.

Conduct experiments to test this framework.


Dan herms department of entomology the ohio state university

Framework: carbon allocation patterns of trees

Herms, D.A. 2002. Effects of fertilization on insect resistance of woody ornamental plants: reassessing an entrenched paradigm. Environmental Entomology 31:923-933.

Herms, D.A. 2001. Resource allocation trade-offs in trees. Arborists News 10(5):41-47.

Herms, D.A. 2001. Fertilization and pest control. Tree Care Industry 12(5):8-10,12,14.

Herms, D.A. 1998. Understanding tree responses to abiotic and biotic stress complexes. Arborist News 7(1):9-15.

Herms, D.A., and W.J. Mattson. 1997. Trees, stress, and pests. pp. 13-25. In J.E. Lloyd, ed. Plant Health Care for Woody Ornamentals, International Society of Arboriculture, Savoy, IL.

Herms, D.A., and W.J. Mattson. 1992. The dilemma of plants: to grow or defend. Quarterly Review of Biology 67(3):283-335.


Different patterns of resource allocation and acquisition work in different environments

Different patterns of resource allocation and acquisition work in different environments


Dan herms department of entomology the ohio state university

  • Concepts to emphasize:

  • resource acquisition vs. resource allocation

  • carbon budgets and allocation tradeoffs

  • integration of above- and below-ground growth

  • acclimation to stressful environments


Dan herms department of entomology the ohio state university

Resource acquisition vs. allocation

(Income vs. budgeting)


Dan herms department of entomology the ohio state university

  • Whole plant carbon budget:

  • photosynthesis rate per unit leaf area

  • total leaf area


Dan herms department of entomology the ohio state university

  • Allocation tradeoffs: plants have limited resources to support:

  • growth

  • maintenance

  • reproduction

  • storage

  • defense


Dan herms department of entomology the ohio state university

  • The chemical arsenal of plants: defense and stress tolerance

  • Tannins

  • Phenolic glycosides

  • Terpenes

  • Alkaloids

  • Cyanogenic compounds

  • Defensive proteins


Dan herms department of entomology the ohio state university

  • Resource allocation patterns

  • In faster growing plants:

  • high allocation to total leaf area

  • high photosynthesis rate

  • lower allocation to root growth

  • lower levels of defensive compounds

  • In slower growing plants:

  • lower allocation to total leaf area

  • high photosynthesis rate

  • higher allocation to root growth

  • higher levels of defensive compounds


Dan herms department of entomology the ohio state university

Computer-controlled fertigation system to study responses of willow to nutrient availability

Glynn et al. (2007) New Phytologist 176:623-634


Dan herms department of entomology the ohio state university

  • Nutrient availability and carbon acquisition:

  • no effect on photosynthesis rate / leaf area

  • increased total leaf area


Dan herms department of entomology the ohio state university

Source / Sink Interactions: carbon moves from sources to sinks via phloem transport


Dan herms department of entomology the ohio state university

  • Mechanisms of photosynthetic acclimation:

  • Nitrogen allocation and specific leaf mass

  • Root:shoot ratios


Dan herms department of entomology the ohio state university

Nitrogen deficiency does not cause chlorosis

in plants that have had time to acclimate to

their environment.

Harris, R. W. 1992. Root-shoot ratios. J. Arboriculture 18: 39-42


Dan herms department of entomology the ohio state university

Stable root:shoot ratios between days 40-85 consistent with equilibrium patterns of resource allocation


Dan herms department of entomology the ohio state university

Soil fertility and insect resistance:

“Properly fertilized trees are better able to ward off

both insect and disease damage."

“Fertilizing landscape plants promotes their general

health and vitality, making them more resistant to

insect and disease attack."

"Fertilization promotes vigorous growth, disease,

and insect resistance, and stress tolerance."


Dan herms department of entomology the ohio state university

Fertilization decreased the insect resistance of woody plants in almost every study.

No study showed increased resistance.

Herms, D.A. 2002. Effects of fertilization on insect resistance of woody ornamental plants: reassessing an entrenched paradigm. Environmental Entomology 31:923-933.


Dan herms department of entomology the ohio state university

Field Studies: Effects of fertilization on paper birch and red pine


Dan herms department of entomology the ohio state university

Fertilizer Treatment (ANSI standard):

Rate:4.1 lb N / 1000 ft2 / yr

200 kg N / ha / yr

178 lb N / acre / yr

Formulation: 18:5:4 NPK (56 % N slow release)

Timing: early May and mid-Sept (split application)


Dan herms department of entomology the ohio state university

Fertilization increased growth of Sphaeropsis tip blight lesions by 50%

Blodgett et al. 2005. Forest Ecology and Management 208:273-382.


Dan herms department of entomology the ohio state university

Effects of nursery fertility regime on crabapple following transplanting

(Lloyd, J.E., et al. 2006. HortScience 41:442-445)

1997: three fertility treatments in container nursery

1998: transplanted to low maintenance landscape.


Dan herms department of entomology the ohio state university

Greater impact of drought stress on photosynthesis of high fertility plants.


Dan herms department of entomology the ohio state university

  • Fertilization and stress tolerance:

  • decreased root:shoot ratio

  • increased water requirements

  • decreased secondary metabolites


Dan herms department of entomology the ohio state university

  • Fertilization decreased drought stress tolerance:

  • Red oak, chestnut oak (Kleiner et al. 1992)

  • American elm (Walters and Reich 1989)

  • Monterey pine (Linder et al. 1987)

  • Red pine (Miller and Timmer 1994)

  • Loblolly pine (Green et al. 1994)

  • Scots pine (Nilsen 1990)

  • Norway spruce (Nilsen 1995)


Dan herms department of entomology the ohio state university

Nutrient cycling in a forest:

the ultimate slow release fertilizer


Dan herms department of entomology the ohio state university

Disrupted nutrient cycles in constructed landscapes


Dan herms department of entomology the ohio state university

Soil quality: the central role of organic matter (SOM)

  • Key determinant of soil structure:

  • oxygen, drainage, water / nutrient holding

  • capacity.

  • Source of essential nutrients for plants.

  • Foundation of soil food web.

  • Continuously depleted and replenished.


Dan herms department of entomology the ohio state university

The living soil:

In an average cup of healthy soil:

Bacteria: 200 billion

Fungi: 60 miles of hyphae

Protozoa: 20 million

Nematodes: 100,000

Arthropods: 50,000

From: S. Frey, Ohio State University


Dan herms department of entomology the ohio state university

Most labile N is tied up by microbes


Dan herms department of entomology the ohio state university

Nutrient Flow: The Central Role of Microbes

Organic Matter

Soil Microbes

Plants


Dan herms department of entomology the ohio state university

Nutrient Cycling in Ornamental Landscapes

Organic

Matter

(Mulch)

Decomposition

Organic N

Fertilizer

Mineralization

Microbial Turnover

Mineral N

(NH4,, NO3)

Microbial

Uptake

Immobilization

Plant Uptake


Dan herms department of entomology the ohio state university

  • Key principles of nutrient cycling theory:

  • Microbes are C limited.

  • Plants are N limited.

  • Microbes out-compete plants for N.

  • High C:N organic matter: greater proportion

  • of N immobilized by microbes.

  • Low C:N organic matter: greater proportion

  • of N released (mineralized) by microbes.


Dan herms department of entomology the ohio state university

Objective:

Establish general principles for predicting effects of diverse sources of organic matter on soil fertility and plant health.


Dan herms department of entomology the ohio state university

  • How does mulch affect nutrient availability? :

  • 1. Is the carbon available? Stability of OM

  • 2. Who gets the nitrogen? C:N ratio of OM


Dan herms department of entomology the ohio state university

Availability of C for microbes: rate of decomposition

Slow

Inorganic mulch (stone, shredded tires)

Softwood bark (mature trees)

Softwood bark (immature trees)

Hardwood bark

Ground wood

Wood chips

Composted yard waste

Sawdust

Composted Manure

Fast


Dan herms department of entomology the ohio state university

  • N available for plants determined by net balance between:

  • N mineralization by microbes.

  • N immobilization by microbes.


Dan herms department of entomology the ohio state university

  • C:N Ratio of OM and Nutrient Availability:

  • C:N ratio > 30:1

  • Microbes N-limited, scavenge N from soil

  • Available N tied up by microbes

  • N available for plants decreases

  • C:N ratio < 30:1

  • N exceeds microbial requirements

  • N release rates increase

  • N available for plants increases


Dan herms department of entomology the ohio state university

Material C:N RatioRecycled pallets125:1Ground pine bark105:1Fresh wood chips 95:1Hardwood bark 70:1Fresh wood chips w/ foliage 65:1Pine straw 64:1Freshly senesced leaves 55:1Composted wood chips 40:1Composted yard waste 17:1Composted manure 12:1


Dan herms department of entomology the ohio state university

  • Case study: effects of mulch on soil microbes, nutrient cycling, and plant health.

  • Recycled organic wastes:

  • Composted yard waste (C:N = 17:1)

  • Ground pallets (C:N = 125:1)


Dan herms department of entomology the ohio state university

Recyled organic

waste as mulch


Dan herms department of entomology the ohio state university

Experimental Mulches

Composted Yard Trimmings

C:N ratio = 17:1

Ground Wood Pallets

C:N ratio = 125:1


Dan herms department of entomology the ohio state university

Composted mulch

Ground wood pallets


Dan herms department of entomology the ohio state university

Experimental approach:


Dan herms department of entomology the ohio state university

Three Mulch Treatments:

1. Composted yard waste (C:N ratio = 17:1)

2. Ground wood pallets (C:N ratio = 125:1)

3. Bare soil control

Each with and without fertilization

(18-5-4 NPK, 3 lbs N / 1000 ft2 / yr)


Dan herms department of entomology the ohio state university

Mulch effects on tree growth


Dan herms department of entomology the ohio state university

Nitrate as signaling molecule: gene expression and regulation of carbon allocation in Arabidopsis:

High soil nitrate:

Up regulation of genes for shoot growth, protein synthesis.

Down regulation of genes for secondary metabolism, root growth.

Low soil nitrate:

Down regulation of genes for shoot growth, protein synthesis.

Up regulation of genes for secondary metabolism, root growth.

Scheible, et al. 2004. Plant Physiology 136:2483-2499.

Zhang and Forde. 2000. Journal of Experimental Botany 51: 51-59.


Dan herms department of entomology the ohio state university

Hypothesis:trees are adapted to the nutrient fluxes and signals associated with gradual decomposition of leaf litter, including low nitrate levels and high organic N sources.

Can trees be tricked into maladaptive allocation patterns?


Dan herms department of entomology the ohio state university

Japanese Beetle

Fall Webworm


Dan herms department of entomology the ohio state university

Trophic cascade from microbes through plants to insect herbivores:

Organic Matter

Microbe Effects on Nutrient Availability

Plant Growth and Defense

Plant-Feeding Insects


Dan herms department of entomology the ohio state university

  • Conclusions:

  • 1. Both mulches increased:

    • soil organic matter

    • microbial biomass and activity

  • 2. Yard waste increased, ground wooddecreased:

    • nutrient availability

    • plant growth

    • susceptibility to insects


Dan herms department of entomology the ohio state university

  • How can mulch applied to the soil surface affect nutrient availability below?

  • Soil homogenization by abiotic and

  • biotic forces (rapid increase in SOM in

  • mulched plots)

  • Subterranean foraging by hyphae of

  • fungi that have colonized the mulch.

  • 3. It just does.


Dan herms department of entomology the ohio state university

  • Consistent with hypotheses:

  • 1. Soil microbes are carbon-limited.

  • 2. Plants are nitrogen limited.

  • Microbes out-compete plants for nitrogen.

  • 4. Competition for N mediated by C:N ratio of OM.

  • 5. Trade-off between growth and defense in plants.


Dan herms department of entomology the ohio state university

  • Prescription mulching:

  • Low C:N mulch (e.g. composted yard trimmings):

  • degraded soils

  • increased plant growth

  • new landscapes

  • High C:N mulch (e.g. recycled pallets):

  • slow to moderate growth

  • established plantings


Dan herms department of entomology the ohio state university

Mulch volcanoes are not good for trees!


Dan herms department of entomology the ohio state university

If you must make volcanoes, at least keep the mulch in the bags


Dan herms department of entomology the ohio state university

Ecological Interactions in Sub-Soil


Dan herms department of entomology the ohio state university

Comparison of Sub-Soil and Top Soil Plots:

Sub Soil Top Soil

Organic Matter (%) 0.75 2.24

Clay (%) 24 17

Total N (ppm) 5601790

Nitrate N (ppm) 8 161

Phosphorus (ppm) 8 50


Dan herms department of entomology the ohio state university

In subsoil:

Fertilization increased growth and decreased phenolic compounds.

In topsoil:

Fertilization had no effect on growth or phenolics.


Dan herms department of entomology the ohio state university

Fertilization effects on fall webworm


Dan herms department of entomology the ohio state university

  • Mycorrhizae research:

  • Root colonization in subsoil

  • Effects of fertilizer

  • Interactions between native and commercial

  • mycorrhizae

Nate Kleczewski


Dan herms department of entomology the ohio state university

  • Allocation to mycorrhizae

  • Benefits:

  • phosphorus acquisition

  • organic nitrogen uptake

  • increased drought tolerance

  • increased resistance to root disease

  • Costs:

  • up to 40% of carbon assimilated by the plant.


Dan herms department of entomology the ohio state university

Symbiosis (living together):

mutualism parasitism

Under some conditions, mycorrhizal fungi act as parasites, taking more than they give.


Dan herms department of entomology the ohio state university

Plants can suppress mycorrhizae when costs exceed benefits:

High nutrient availability

(should mycorrhizal spores be applied with fertilizer?)

Low carbon availability (e.g. shade, defoliation)


Dan herms department of entomology the ohio state university

Questions regarding commercial mycorrhizae:

  • Will they establish?

  • Will they compete with native mycorrhizal fungi?

  • Will they enhance plant growth and survival?


Dan herms department of entomology the ohio state university

Key Findings:1. Only native EMF were detected.2. No difference between top-soil and sub-soil.

*

* Estimated number of viable propagules


Dan herms department of entomology the ohio state university

Key Findings:3. High fertility suppressed mycorrhizae.

*


Dan herms department of entomology the ohio state university

Key Findings:1. Only native EMF were detected.2. No difference between top-soil and sub-soil.3. High fertility suppressed mycorrhizae.


Dan herms department of entomology the ohio state university

  • Conclusions:

  • Increased soil fertility:

  • Increases growth

  • Decreases chemical defenses

  • Decreases root:shoot ratio

  • Can decrease pest resistance

  • Can decreases drought stress tolerance


Dan herms department of entomology the ohio state university

  • Effects are independent of nutrient source, form, or timing:

  • container fertigation

  • conventional fertilization (ANSI guidelines)

  • stored nutrients obtained the previous year

  • mulch effects on soil microbes and nutrient cycling

  • inherently fertile vs. infertile soil.


Dan herms department of entomology the ohio state university

  • This doesn’t mean:

  • fertilization is bad.

  • fertilization will increase pest problems in landscapes

  • (these studies haven’t been done yet).

This does mean:

The data do not support the conventional wisdom that fertilization increases pest resistance.


Dan herms department of entomology the ohio state university

  • The Natural Tree Environment:

  • nutrient limited soils

  • frequent episodes of drought stress

  • insects and pathogens

  • The Natural Tree Response:

  • high root:shoot ratios

  • high levels of storage carbohydrates

  • high levels of defensive chemicals

  • moderate growth


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